Package Exports

@datadog/wasm-js-rewriter
@datadog/wasm-js-rewriter/js/source-map
@datadog/wasm-js-rewriter/js/source-map/index.js
@datadog/wasm-js-rewriter/js/stack-trace
@datadog/wasm-js-rewriter/js/stack-trace/index.js
@datadog/wasm-js-rewriter/main.js

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (@datadog/wasm-js-rewriter) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

dd-wasm-js-rewriter

Node.js native AST rewriter heavily based on Speedy Web Compiler o SWC compiler used to instrument Javascript source files.

Workflow

Parse Javascript code to obtain the AST
Replace certain AST expressions -> Currently it is focused in certain operators like + and +=, template literals and some String methods
Generate the new Javascript code as from the modified AST -> In addition to the Javascript code, the corresponding source map is returned chaining it with the original source map if necessary.

Usage

const Rewriter = require('@datadog/wasm-js-rewriter')

const rewriter = new Rewriter(rewriterConfig)
const result = rewriter.rewrite(code, filename)

Configuration options

RewriterConfig {
  // enable/disable sourceMap chaining - false by default
  chainSourceMap?: boolean

  // enable/disable comments printing - false by default
  comments?: boolean

  // establishes the prefix for the injected local variables - 6 random characters by default
  localVarPrefix?: string

  // sets the list of methods or operators to be rewritten
  csiMethods?: Array<CsiMethod>

  // extracts hardcoded string literals - true by default
  literals?: boolean
}

CsiMethod {
  // name of the String method to rewrite
  src: string

  // optional name of the replacement method. If not specified a convention shall be used
  dst?: string

  // indicates if it is an operator like +
  operator?: boolean
}

Example

const Rewriter = require('@datadog/wasm-js-rewriter')

const rewriterConfig = {
  csiMethods: [{ src: 'substring' }],
  localVarPrefix: 'test',
}

const rewriter = new Rewriter(rewriterConfig)

const code = `function sub(a) {
  return a.substring(1)
}`
const result = rewriter.rewrite(code, filename)

console.log(result.content)
/*
function sub(a) {
  let __datadog_test_0, __datadog_test_1;
  return (__datadog_test_0 = a, __datadog_test_1 = __datadog_test_0.substring, _ddiast.stringSubstring(__datadog_test_1.call(__datadog_test_0, 1), __datadog_test_1, __datadog_test_0, 1));
}
*/

Local setup

To set up the project locally, you should install cargo and wasm-pack:

$ curl https://sh.rustup.rs -sSf | sh

$ cargo install wasm-pack

and project dependencies:

$ npm install

Build

Build the project with

$ npm run build

It will compile WASM binaries by default and then it will be possible to run the tests with

$ npm t